Was under contract but buyers backed out after mold air test came back positive.  

Is the house have forced hot air as its heating source?

Worse case, you may need to blow air through the lines to force the water out.You can always hire a plumber or PM company to winterize the house for you.

I  have a question, I found a vacant building in fish town the owner is decease but I found out who the next air is. but i'm having a hard time location that person. what should i do????

would an air compressor do the trick?  

The central air is nice but being in a C area when and if your unit is vacant how sure are you that you won't have the unit stolen. 

Any BP members with any VRBO or air BNB offerings I can give some business to?

Some apartments will be hot like .... and others will cry.Most brooklyn apartment buildings are one pipe and each radiator have an air valve.

As for the ground it's hard to tell because there is a flower bed along that wall, but the air conditioner and its concrete pad are close. 

I am going to pull $20,000 out of thin air and use it for this example.$300,000 (what you can sell it for after updating) - $20,000 (hypothetical expense number pulled out of thin air) - $180,000 (what you owe) = $100,000x.02 if it were in a low interest account = $2,000.